Hexagon (decode): look for pkts with multiple insns at the same slot

Each slot in a packet can be assigned to at most one instruction.
Although the assembler generally ought to enforce this rule, we better
be safe than sorry and also do some check to properly throw an "invalid
packet" exception on wrong slot assignments.

This should also make it easier to debug possible future errors caused
by missing updates to `find_iclass_slots()` rules in
target/hexagon/iclass.c.

Co-authored-by: Taylor Simpson <tsimpson@quicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Tested-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <f8b829443523568823d062adf8bf6659bc6d4a3f.1683552984.git.quic_mathbern@quicinc.com>

diff --git a/target/hexagon/decode.c b/target/hexagon/decode.c
index 041c8de751b4e931d1f4ef169ca225306a06cd33..946c55cc71da2ea2b80a9e5f8c2a5aa1b32a71d7 100644 (file)
--- a/target/hexagon/decode.c
+++ b/target/hexagon/decode.c
@@ -1,5 +1,5 @@
 /*
- *  Copyright(c) 2019-2022 Qualcomm Innovation Center, Inc. All Rights Reserved.
+ *  Copyright(c) 2019-2023 Qualcomm Innovation Center, Inc. All Rights Reserved.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -797,7 +797,26 @@ static bool decode_parsebits_is_loopend(uint32_t encoding32)
     return bits == 0x2;
 }
 
-static void
+static bool has_valid_slot_assignment(Packet *pkt)
+{
+    int used_slots = 0;
+    for (int i = 0; i < pkt->num_insns; i++) {
+        int slot_mask;
+        Insn *insn = &pkt->insn[i];
+        if (decode_opcode_ends_loop(insn->opcode)) {
+            /* We overload slot 0 for endloop. */
+            continue;
+        }
+        slot_mask = 1 << insn->slot;
+        if (used_slots & slot_mask) {
+            return false;
+        }
+        used_slots |= slot_mask;
+    }
+    return true;
+}
+
+static bool
 decode_set_slot_number(Packet *pkt)
 {
     int slot;
@@ -886,6 +905,8 @@ decode_set_slot_number(Packet *pkt)
         /* Then push it to slot0 */
         pkt->insn[slot1_iidx].slot = 0;
     }
+
+    return has_valid_slot_assignment(pkt);
 }
 
 /*
@@ -961,8 +982,11 @@ int decode_packet(int max_words, const uint32_t *words, Packet *pkt,
     decode_apply_extenders(pkt);
     if (!disas_only) {
         decode_remove_extenders(pkt);
+        if (!decode_set_slot_number(pkt)) {
+            /* Invalid packet */
+            return 0;
+        }
     }
-    decode_set_slot_number(pkt);
     decode_fill_newvalue_regno(pkt);
 
     if (pkt->pkt_has_hvx) {

diff --git a/tests/tcg/hexagon/Makefile.target b/tests/tcg/hexagon/Makefile.target
index 6109a7ed10b315df44a6b13163ad9365cc84d26d..890cceed5ded433db137ec70d79926abcce5d035 100644 (file)
--- a/tests/tcg/hexagon/Makefile.target
+++ b/tests/tcg/hexagon/Makefile.target
@@ -50,6 +50,13 @@ HEX_TESTS += vector_add_int
 HEX_TESTS += scatter_gather
 HEX_TESTS += hvx_misc
 HEX_TESTS += hvx_histogram
+HEX_TESTS += invalid-slots
+
+run-and-check-exception = $(call run-test,$2,$3 2>$2.stderr; \
+       test $$? -eq 1 && grep -q "exception $(strip $1)" $2.stderr)
+
+run-invalid-slots: invalid-slots
+       $(call run-and-check-exception, 0x15, $@, $(QEMU) $(QEMU_OPTS) $<)
 
 HEX_TESTS += test_abs
 HEX_TESTS += test_bitcnt

diff --git a/tests/tcg/hexagon/invalid-slots.c b/tests/tcg/hexagon/invalid-slots.c
new file mode 100644 (file)
index 0000000..366ce4f
--- /dev/null
+++ b/tests/tcg/hexagon/invalid-slots.c
@@ -0,0 +1,29 @@
+/*
+ *  Copyright(c) 2023 Qualcomm Innovation Center, Inc. All Rights Reserved.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+char mem[8] __attribute__((aligned(8)));
+
+int main()
+{
+    asm volatile(
+        "r0 = #mem\n"
+        /* Invalid packet (2 instructions at slot 0): */
+        ".word 0xa1804100\n" /* { memw(r0) = r1;      */
+        ".word 0x28032804\n" /*   r3 = #0; r4 = #0 }  */
+        : : : "r0", "r3", "r4", "memory");
+    return 0;
+}